Searching for Earths

October 1, 2007

By Dr. David Rogstad

I once saw a toy that served as a visual example of the saying "one in a million". It consisted of a clear plastic ball about 4 inches in diameter filled with literally a million little plastic cubes. All were painted silver but one, which was painted red. The object was to find the red cube! Needless to say, finding it was no mean task.

Searching for Earth-like planets revolving around stars other than our sun (exoplanets) presents an even more difficult task. The parent star will typically be more than a billion times as intense as the planet with a separation of only a few tenths of a second of arc (a very narrow angle as measured from Earth). The ultimate goal of the researcher is not only to find a planet in this environment but to get enough information about the planet to tell if it can harbor life. Some have likened it to searching for and photographing a firefly in the face of a searchlight.

For any planet revolving about a star, the planet reflects some light from the star. In addition the planet will give off some thermal emission because it is being heated by the star. Both of these forms of light can be captured with a telescope that can detect the spectrum of this light. The figure below shows what a spectrum of the Earth would look like from some distance away using such an instrument. If a researcher can get a similar spectrum of the exoplanet, he can be reasonably certain that life could exist on that planet. The goal, of course, is to establish that we are not alone.

A NASA project called the Terrestrial Planet Finder (TPF) will launch into orbit two observatories for capturing the reflected and thermally emitted light from terrestrial (Earth-like) exoplanets. One uses coronagraphic imaging (TPF-C), which incorporates a mask to block out the light coming from the parent star. The other uses interferometric imaging (TPF-I) to eliminate its light. Both techniques require exquisitely fine-tuned optics to successfully reject the star light and image the planet. The TPF will have 100 times the imaging power of the Hubble Space Telescope. Plans call for launching the TPF-C around 2014 and the TPF-I before 2020.

How do the scholars at Reasons To Believe view this research from a creation-model perspective? We encourage ongoing research as the way to determine scientific truth. "Test everything," the Scripture says (1 Thessalonians 5:21), so we adopt this position in our study of the cosmos. It is our expectation, however, that as more information becomes available, the truth of God's word (and the creation model derived from it) will gain further support. We expect that scientific advance will further establish the uniqueness of the Earth as an advanced life site, and for the purposes God has revealed in the Bible.

Subjects:
Extrasolar Planets, Habitable Planets, Instrumentation, Life on Other Planets

Dr. David Rogstad

Dr. Dave Rogstad received his PhD in physics from Caltech and worked over 30 years for NASA’s Jet Propulsion Laboratory. Though now retired, Dave continues to serve as an RTB board member and participates regularly in several RTB podcasts.

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